The present invention, as with the inventions in the previously mentioned patent applications, relates to apparatus systems and methods for running and storing pipe used in the drilling and completion of wells.
Currently, pipe used in drilling and completing wells is stored in the derrick or stored in racks on the drilling structure. When the pipe is being temporarily removed from the well, it is pulled from the well in stands of three or four joints and stored vertically in the derrick. Going back into the well, the process is reversed.
When using a top drive or traveling block to run pipe in and out of the well, the time required to come out of the well includes the time required to attach to the top of the drill string, pull a stand up above the floor, unthread the stand, set it back in the derrick, and return the top drive or traveling block down to the floor to engage the drill string to pull another stand.
In an invention described in the previously identified patent applications, the pipe used to drill and complete an offshore well is run into and out of the well in a continuous string of jointed pipe sections. The water area surrounding the drilling structure is used to store the pipe in a continuous string or in a series of relatively long string segments. The pipe string is conveyed through a curved guide extending from the drilling rig to the water area adjacent the drilling structure. The radius of curvature of the guide is greater than the minimum permitted non-yielding radius of curvature for the stiffest string of pipe to be used in the drilling or completion of the well.
The large drill pipe used to drill wells in deep water can have a cross sectional diameter of 6 ⅝ inches or larger. A curved guide capable of handling such drill pipe preferably has a radius of curvature of approximately 160 ft. The distance from the point on the drilling rig floor at which the pipe exits the well to the point at which the pipe is redirected back into the water is therefore approximately 320 ft. Very large drill ships have adequate room to accommodate the required 320 ft. spacing between the drilling rig floor and the water entry point. Such is not the case in smaller rigs such as semi-submersible rigs.
The distance from the rotary table to the furthest edge of a semi-submersible drilling structure is typically less than 200 ft. One object of this invention is to adapt the pipe handling system, method and apparatus described in the previously identified applications for use on a semi-submersible rig.
It may be desirable to maintain circulation through the string of pipe stored in the sea. It may also be desirable to displace the drilling fluid contained within the drill pipe before it is stored in the sea.
Very long strings of pipe inserted into a storage sleeve may require a means for assisting the insertion of the drill string into the sleeve.
It may also be desirable to have multiple strings of pipe stored in the sea with multiple systems available for separately, or simultaneously, supplying the strings to the drilling rig floor. Such is the case, for example, when two completion strings are simultaneously run into the well in what is termed a xe2x80x9cdual completion.xe2x80x9d
Drilling structures that lack sufficient deck space to accommodate a large bending radius guide are provided with a platform extension to position a work area at the location where the string completes its 180-degree curve and extends vertically into the water. In a preferred embodiment, the platform extension is positioned at one corner of a four-cornered deck of a semi-submersible drilling rig to minimize the length of the platform required to extend to the point of the completion of the drill pipe curve.
Multiple guides may be employed for simultaneously running two strings of pipe. The string may be stored in one or more long sections or in a single continuous string. The major portions of the string or long pipe sections may be stored below the surface of the water. Provision is made for pumping fluids through the pipe string, and/or the pipe sections stored in water, to the well. The string may be stored in a sleeve. A flexible hose attached to the end of the drill string permits pumping of fluids into the well through the string while the string is in the sleeve. An air supply to the sleeve assists in maintaining the buoyancy of the sleeve and its contents. A pulling system is provided to assist in pulling the drill string through the sleeve.